From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [linux-pm] Re: [patch] hibernation: utilize ACPI hardware signature Date: Wed, 2 Jan 2008 23:01:45 +0100 Message-ID: <200801022301.45706.rjw@sisk.pl> References: <1199257162.14632.4.camel@sli10-desk.sh.intel.com> <200801021505.39789.rjw@sisk.pl> <477C019D.1070001@nigel.suspend2.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:43776 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754125AbYABV7x (ORCPT ); Wed, 2 Jan 2008 16:59:53 -0500 In-Reply-To: <477C019D.1070001@nigel.suspend2.net> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: nigel@nigel.suspend2.net Cc: Shaohua Li , linux acpi , pm list , Pavel Machek On Wednesday, 2 of January 2008, Nigel Cunningham wrote: > Hi. > > Rafael J. Wysocki wrote: > > On Wednesday, 2 of January 2008, Shaohua Li wrote: > >> ACPI defines a hardware signature. BIOS calculates the signature > >> according to hardware configure, if hardware changes, the signature will > >> change, in this case, S4 resume should fail. > > > > The idea is fine, but I'd prefer to do that in a more straightforward way. > > Namely, we can just: > > * write the signature into a variable in, for example, > > acpi_hibernation_prepare() (then, the "old" signature value will be > > automatically saved in the image) > > * compare it with a the "new" value read from the BIOS in > > acpi_hibernation_leave() and panic if there's a mismatch > > * add a configuration option to disable this behavior (just in case) > > This way we can avoid modifying the entire generic interface to add the feature > > specific to ACPI. > > > > Still, if you want the boot kernel to check the signature, which will be more > > elegant (but please note that on x86-64 the boot kernel need not support ACPI > > at all), you can use the (recently introduced) architecture part of the image > > header for this purpose, without modifying the generic interface. > > I suppose we can always disable this when we start to support hardware > changing over hibernate (I have ideas in this direction - memory cold > plugging, for a start). Well, if we support such features, we won't be following ACPI any more. Greetings, Rafael